1. Field of the Invention
The present invention relates to a control apparatus for an engine. More specifically, the present invention relates to a control apparatus for an engine that controls the opening and closing timings of the intake and exhaust valves and the fuel injection timing in order to promote vaporization of the fuel.
2. Background Information
When a cold engine is initially started and in a warm up operation, the fuel being injected from a fuel injection valve into an intake path cannot be vaporized easily because its temperature is low. Accordingly, the fuel stays in a liquid form and adheres to a wall surface of the intake path. Therefore, the fuel cannot be supplied to the combustion chamber in a stable manner. This results in unstable combustion of the fuel. Also, the discharge of HC in the exhausted emission increases. Furthermore, in order to compensate for the amount of fuel being injected as a liquid, the amount of fuel being injected has to be increased. Therefore, the amount of fuel consumption increases. To solve this problem, it has been proposed to use special fuel injection valves. For example, fuel injection valves having a porous plate or that inject fuel along with a part of the intake air that have been proposed.
On the other hand, in the technology disclosed in Japanese Laid-Open Patent Application Publication No. 6-323168, the open-valve timing of the intake valve is delayed while the engine is cold by using a variable valve timing apparatus that can freely control the opening and closing timings of the exhaust valve. In this manner, a pressure differential is generated between the combustion chamber and the intake path. By making the intake speed of the fuel high, the vaporization of the fuel is promoted.
In view of the above, there exists a need for an improved control apparatus for an engine that improves vaporization of fuel while overcoming the deficiencies in the prior art. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.
In the technology disclosed in Japanese Laid-Open Patent Application Publication No. 6-323168, the above-mentioned pressure differential can be obtained at the time of cranking when the engine is started. However, after the negative pressure permeates inside the intake path, no differential pressure is generated between the combustion chamber and the intake path even when the open-valve timing of the intake valve is delayed. Therefore, the intake speed of the fuel cannot be increased. Accordingly, the effect of promoting the vaporization of the fuel does not last.
The present invention has been conceived in view of the above-described situation. The control apparatus of the present invention is designed to control the engine so as to prevent an increase in the discharge of HC in the exhaust emission, as well as prevent an increase in the fuel consumption. This is accomplished in the present invention by sustaining the promotion of vaporization of the injected fuel while the engine is being warmed up.
An aspect of the present invention is to provide a control apparatus for an engine comprising intake and exhaust passages fluidly coupled to a combustion chamber, an intake valve arranged to open and close the intake passage to the combustion chamber, an exhaust valve arranged to open and close the exhaust passage to the combustion chamber, and a fuel injection valve arranged to inject fuel into the intake passage. The intake valve is arranged to open and close the intake passage to the combustion chamber. The intake valve has opening and closing timings with the opening timing of the intake valve being set to open the intake valve after an exhaust top dead center such that a first crank angle is measured between the exhaust top dead center and the opening timing of the intake valve. The exhaust valve is arranged to open and close the exhaust passage to the combustion chamber. The exhaust valve has opening and closing timings with the closing timing of the exhaust valve being set to close the exhaust valve before an exhaust top dead center such that a second crank angle is measured between the closing timing of the exhaust valve and the exhaust top dead center. The second crank angle is greater than the first crank angle. The fuel injection valve is arranged to inject fuel into the intake passage. The fuel injection valve has a fuel injection timing set to inject fuel after opening of the intake valve.
These and other objects, features, aspects and advantages of the present invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses a preferred embodiment of the present invention.